As already known in the prior art, cooling systems function with coolant gas compressors that make a lot of noise while they are operating, rendering the search for ways of attenuating the noise a constant work.
With basis on the fundamentals of acoustics, it is known that the sound can be defined as a very fast pressure changes which travels in the form of waves in an elastic medium and, generally, it is caused by the vibration of an elastic body, which generates a corresponding pressure change in the surrounding medium. The sound can be represented by a sine wave, described as a circular movement which travels along an axle—which may represent a distance or time, for example—and the relation of such movement to a reference point is named phase.
The sound wave cancellation occurs when two waves having the same frequency, despite a phase difference of 180 degrees, reach one another at a certain position. When this phenomenon occurs said two waves are cancelled, reducing, then, the noise at this certain frequency. Therefore, if two waves having the same frequency, being 180 degrees out of phase, reach one another, said waves will be cancelled and the total cancellation will occur when the amplitude of the waves are equal. On the contrary, the waves will be only partially cancelled.
The object of document U.S. Pat. No. 5,125,241 is based on the principle of sound wave cancellation for attenuating the noise produced by the compressor involving, however, a plurality of electrical and electronic components—such as sensors, microphones and loudspeakers, for example—which renders the constructive system extremely complex and, consequently, expensive.
Document KR960003388 reveals a main inlet pipe folded in a specific angle and provided with a plurality of openings, which settles, in its interior, a second pipe for attenuating the sound by utilizing the concept of phase cancellation. It is noted, however, that this configuration is also significantly complex, being also expensive, besides subjecting the apparatus to the occurrence of problems that may demand a frequent maintenance.